Simulation Study Of Key Reactions During Hydrothermal Liquefaction Of Lignite Model Compound In CO Atmosphere

China is rich in coal resources,of which lignite accounts for 13%and the development of lignite conversion technology has broad prospects.The high content of water,oxygen and inorganic minerals in lignite has greatly hinders its application in traditional industrial processes such as coking and gasification.Therefore,it is generally directly burned as low-calorie fuel,which not only pollutes the environment,but also causes waste.Lignite has chemical activity and reactivity,which can be used as a suitable raw material for direct liquefaction.Hydrothermal liquefaction under carbon monoxide atmosphere is considered as a promising alternative technology for direct liquefaction of lignite.In this thesis,the process of water gas shift reaction with non-catalytic and typical catalysts and the production of active species H^-under hydrothermal conditions,as well as the process of deoxidation between active species H^-and lignite model compounds are studied by density functional theory.At the level of M06-2X/6-311++G（d,p）,the process of water-gas shift reaction and the formation of active species H^-with non-catalyzed and typical catalysts under hydrothermal conditions were studied.Under the condition of OH^-catalysis,the water-gas shift reaction is more suitable in the aqueous phase.The reaction path of the reaction between CO and OH^-was studied,and its highest energy barrier was 195.05k J/mol.Compared with the possible H active species H^-,H^·and H⁺,it was determined that the active species H catalyzed by OH^-in the hydrothermal environment of CO atmosphere was H^-.Using the method of TPSS,6-311++G（d,p）is used for C,O,H and Cl,and SDD and its effective core potential are used for Fe and Ni.And the chemical valence states of Fe and Ni are determined by LOBA analysis.The energy of four carbonyl compounds or carbonyl chloride in the reaction was studied.Under the same metal,with the increase of the valence state of metal ions.The difference is that with the increase of the valence state of Fe,the energy barrier of the transfer of H to Fe increases.The valence state of Ni increases,and the energy barrier of H transfer to Ni decreases.It is impossible to produce H⁺.Using Ni（CO）₄as catalyst,the active species produced is H^-.Using Fe（CO）₅,Fe（CO）₃Cl₂ and Ni（CO）₂Cl₂ as catalysts,the active species produced is H^·,among which Ni（CO）₂Cl₂ as catalyst has the lowest dissociation energy.The deoxygenation activity of three kinds of H species to phenol was studied,which was H^·>H^->H⁺.CO and OH^-react to produce H^-,then hydrodeoxygenation of phenol and other lignite model compounds,and benzene and other aromatic hydrocarbons or aliphatic hydrocarbons are obtained.The OH^-are also recovered,thus triggering the next catalytic cycle.A catalytic cycle is also designed for the active species H^·.The degree of difficulty in deoxygenation of between H^-and lignite model compounds was studied.It was found that the more the number of polycyclic aromatic hydrocarbons,the lower the LUMO orbital energy and the lower the reaction energy barrier.For H^·,the more ring numbers of polycyclic aromatic hydrocarbons,the higher the difficulty of deoxygenation.In the process of phenol deoxygenation,the energy barrier of benzene ring hydrogenation is low,but the cyclohexanol deoxygenation is difficult after hydrogenation,and its energy barrier is higher than phenol deoxygenation.Thermochemical analysis shows that the reaction of active species H^·or H^-with phenol is an exothermic reaction,and the reaction of active species H^-with phenol releases more heat than that of H^·.These results provide valuable information for the future study of OH^-catalyzed deoxygenation of lignite in CO atmosphere.It is helpful to study the hydrothermal deoxygenation of lignite and other related processes.